Pianosakm2) island in Italy's Tuscan Archipelago. The name derive from the Italian word "pianura" (plain), since its highest point is some 22 meters over sea level.
Pianosa has no stable residents. It is mildly famous in Italy for hosting a maximum-security prison, where especially dangerous Mafia criminals are held.
For administration purpose, Pianosa is under Elba island municipality. On clear days, it can bee seen from that island as a dark blue line over the ligher blue sea.